454 DH. W. G. EIDEWOOD ON THE HYOBEANCHIAL 



On the Hyobrancbial Skeleton and Larynx of the new Aglossal 



Toad, Hymenochirus Boettgeri. By W. G. Eidewood, 



D.Sc, F.L.S., Lecturer on Biology at St. Mary's Hospital 

 Medical School, London. 



[Bead 2nd November, 1899.] 



(Plate 31.) 



Xenopvs and Pipa have for many years been to herpetologists a 

 fruitful source of discussion, by reason of the structural peculi- 

 arities which mark them off so sharply from the other Anura, and 

 also on account of the great differences which exist between them- 

 selves. They are isolated types which fail to show any marked 

 affinity with any of the Phaneroglossal Anura, and the relatively 

 few features in which they resemble one another some writers 

 would explain away as due to convergence and adaptation to 

 similar conditions of life. The discovery of a third genus of 

 Aglossal Toads marks the beginning of a new era in the history 

 of this little suborder ; and it is to Hymenochirus that attention 

 will now be turned with the object of ascertaining how far the 

 Anura Aglossa constitute a natural assemblage. 



A single specimen of this new form was discovered in 1896 at 

 Ituri, in German East Africa, and was described by Tornier as 

 Xenopus Boettgeri (7. p. 163). Several specimens have since 

 been collected from the Benito river, in the French Congo ; and 

 the skeletal and other characters detailed by Boulenger in the 

 present year (2) go to show that this writer was fully justified in 

 the claim which he put forward in 1896 (1) that Tornier's new- 

 species of Xenopus was entitled to generic rank. 



Having already made an exhaustive study of the hyobrancbial 

 skeleton and larynx of Xenopus and Pipa (4), I applied to 

 Mr. Boulenger for permission to examine these parts in one of 

 the specimens of Hymenochirus belonging to the Natural History 

 Museum. The request was graciously acceded to, and a male and 

 a female specimen were placed at my disposal. For these my 

 thanks are hereby gratefully tendered. 



There are certain features in the hyobrancbial and laryngeal 

 skeleton of Xenopus and Bipa which may be regarded as dis- 

 tinctive, occurring in both of these genera and not in any of the 

 Phaneroglossal Anura. The features in question are : — 



